Add more rules to be able to exclude Prom Operator CRDs

[maxlemieux]

Adding this request to track customer feedback.

Add more rules to be able to exclude Prom Operator CRDs. This is possible with custom configuration today, but would be nice to have a convenient setting to exclude specific prometheus-operator CRs by simply labelling them.

Example rules:

mimir.rules.kubernetes "prometheusRules" {
  address = "https://prometheus-prod-36-prod-us-west-0.grafana.net/"
  basic_auth {
    username = "0000000"
    password = "redacted"
  }
  rule_selector {
    match_expression {
      key = "skip_grafana_cloud"
      operator = "NotIn"
      values = ["true"]
    }
  }
}